This application claims the priority of German Patent Application DE 202 04 085.2 filed Mar. 13, 2002, which is incorporated herein by reference.
The invention relates to a device for producing milk froth for cappuccino.
In a known device of this type (EP 0 858 757 A1), which is connected to an espresso machine and utilizes the machine""s steam generator, a nozzle arrangement having a vacuum chamber is disposed downstream of a steam supply line, and a steam-nozzle opening opens into this arrangement. At the vacuum-chamber exit opposite the steam-nozzle opening, the vacuum chamber is nearly conically tapered, and terminates in a single bore serving as a calming segment. A supply line for an air-milk mixture terminates in a cylindrical segment of the vacuum chamber, between the steam-nozzle opening and the vacuum-chamber exit. The pre-mixing chamber is notably cylindrical, has a larger diameter than the supply line for the air-milk mixture, and is connected to an air conduit and a milk supply line. In this pre-mixing chamber, first an air-milk mixture is formed, which then flows into the vacuum chamber. There, steam is added, which creates the vacuum in the vacuum chamber. The resulting steam-air-milk mixture then flows through the calming segment, in which it is compressed and settled, so it exits the calming segment as milk froth, with the desired consistency.
The diameter-to-length ratio of the single bore forming the calming segment is preferably 1:10.
To attain a satisfactory calming effect of the steam-air-milk mixture with a sufficient throughput, the calming segment is relatively long with respect to the other elements of the device, including the dimensions of the vacuum chamber.
It is therefore the object of the present invention to provide a compact device of the type generally described above, with which a steam-air-milk mixture can be produced as milk froth with the desired consistency.
The above object generally is accomplished according to the invention, by a device for producing milk froth for cappuccino, comprising: a nozzle arrangement that is disposed downstream of a steam supply line, and containing a mixing vacuum chamber into which a steam-nozzle opening opens, and in which an air-milk-mixture supply line, leading from a pre-mixing chamber, terminates, with the pre-mixing chamber being connected to an air conduit and to a milk supply line; and wherein: the nozzle arrangement further includes a calming portion disposed an exit of the vacuum-chamber, with one end of the calming portion forming at least one discharge opening for releasing a steam-air-milk mixture from the mixing vacuum-chamber to the outside; and the calming portion comprises a plurality of calming conduits that have a parallel flow direction, and that each form a respective discharge opening at one open end for discharging a steam-air-milk-mixture partial flow to the outside.
Accordingly, the calming segment is no longer formed from a single bore. Instead, it comprises a plurality of calming conduits, which possess a parallel flow direction. Their intakes are connected to one another at the vacuum-chamber exit, and all of the exits of the calming conduits are open and thereby represent discharge openings for the produced steam-air-milk mixture or the milk froth. Furthermore, the calming conduits are preferably disposed essentially parallel to one another to create an especially compact arrangement.
According to a feature of the invention, it can suffice to provide at least three calming conduits having a parallel flow direction and identical flow cross-sections, and advantageously the conduits are spaced from one another. These conduits divide the steam-air-milk mixture that has been produced in the vacuum chamber into partial flows at the exit of the chamber, with the number of partial flows corresponding to the number of calming conduits. The diameter of each calming conduit is fairly small, so its length can likewise be relatively small in order to achieve a desired diameter-length ratio for compressing and calming the steam-air-milk mixture. Thus, the component encompassing the calming conduits can be compact.
The process of mixing the steam-air-milk mixture that flows from the mixing vacuum chamber has already been completed by the time the mixture enters the calming conduits, particularly because no flow line of a calming conduit is connected to a flow line of an adjacent calming conduit. For this reason, the mixture is effectively calmed in the calming conduits. A further advantage of dividing the calming portion into a plurality of conduits, each having a significantly smaller cross-section than a single calming conduit, is that this arrangement acts as a bubble sieve, which prevents the escape of larger foam bubbles that are formed during the mixing process in the vacuum chamber, and therefore results in an especially fine-pored and stable milk froth.
In accordance with one embodiment of the invention, the vacuum-chamber exit comprises solely the calming conduits having a parallel flow direction. That is, no further structures that influence the flow are interposed between the vacuum chamber and the calming conduits.
To this end, the device is formed with a cylindrical space in the nozzle arrangement, which encompasses the mixing vacuum chamber and the calming conduits that constitute its exit.
This feature makes the device simple to produce.
To further simplify production, the conduits can be formed out of a filling core that is produced separately from the nozzle arrangement, and then inserted into a lower portion of the cylindrical space in the nozzle arrangement.
A further advantage is that the filling core can easily be removed from the lower segment of the cylindrical space, for example for the purpose of cleaning or replacement.
It is further advantageous in terms of manufacture and maintenance for the calming conduits to be formed in the outer surface of the cylindrical filling core, coaxially with respect to its axis of rotational symmetry, and with equidistant spacing around the circumference. It is pointed out here that, after the filling core has been inserted, its axis of rotational symmetry coincides with that of the cylindrical space of the nozzle arrangement.
In a modification of the invention, the filling core can be formed with a cylindrical main portion and a dome-shaped end portion that faces the vacuum chamber after the core has been installed in the chamber. In this case, the calming conduits, having been formed in the outer surface of the cylindrical main portion, extend further toward the dome-shaped end with an elliptical depression. This depression thus extends in the direction of the center axis or the axis of rotational symmetry of the filling core, which attains a uniform, satisfactory flow into the calming conduits.
To achieve the aforementioned bubble-sieve effect, and therefore the desired consistency of the steam-air-milk mixture exiting the calming portion as milk froth, despite the compact, short embodiment of the calming portion, the clear diameter of each calming conduit should not exceed an amount comprising the diameter-length ratio of the calming portion of 1 to at least 10, divided by the number of calming conduits making up the calming portion.
As mentioned above, the steam-air-milk mixture is already completely mixed when it enters the calming conduits. The homogeneous mixing is performed by the pre-mixing chamber, as well as an embodiment of the device, in which the steam nozzle opening in the nozzle arrangement is disposed at an upper, first end of the vacuum chamber, which is located opposite the lower, second end of the vacuum chamber, where the vacuum-chamber exit with the calming conduits is located. In this arrangement of the nozzle opening, the air-milk mixture, which is suctioned, pre-mixed, into the vacuum chamber via a preferably nozzle-shaped line, is thoroughly mixed with the steam exiting the nozzle opening via a large portion of the vacuum chamber.